Minimally-invasive surgery (MIS), such as laparoscopic surgery, involves techniques intended to reduce tissue damage during a surgical procedure. For example, laparoscopic procedures typically involve creating a number of small incisions in the patient (e.g., in the abdomen), and introducing one or more surgical tools (e.g., end effectors and endoscope) through the incisions into the patient. The surgical procedures may then be performed using the introduced surgical tools, with the visualization aid provided by the endoscope.
Generally, MIS provides multiple benefits, such as reduced patient scarring, less patient pain, shorter patient recovery periods, and lower medical treatment costs associated with patient recovery. Recent technology development allows more MIS to be performed with robotic systems that include one or more robotic arms for manipulating surgical tools based on commands from a remote operator. A robotic arm may, for example, support at its distal end various devices such as surgical end effectors, imaging devices, cannulae for providing access to the patient's body cavity and organs, etc. In robotic MIS systems, it may be desirable to establish and maintain high positional accuracy for surgical instruments supported by the robotic arms.
New class of surgical instruments supported for robotic arms may share similar designs, for example, a tool may have an end effector that comprises a robotic wrist and one or more jaws, and a pulley and cable system for coupling the end effector to actuators in a tool drive, which can drive multi-axial motions (e.g., pitch and yaw) of the end effector. The end effectors may include more than one jaws actuated through antagonistic cables to perform grasping, cutting, suturing, among other surgical tasks. The ability to control the grip force between the jaws, while moving the robotic wrist to any angular position with precision, is a fundamental requirement for the usability of the robotic surgical instruments. There is currently no known method that can achieve this with a four-wire antagonistic robotic wrist.